In the manufacture of paper products such as tissues, towels, wipers and the like, a wide variety of product characteristics must be given attention in order to provide a final product with the appropriate blend of attributes suitable for the product's intended purpose. Among these various attributes, improving surface feel, strength, absorbency, bulk and stretch have always been major objectives. Traditionally, many of these paper products have been made using a wet-pressing process in which a significant amount of water is removed from a wet laid web by pressing or squeezing water from the web prior to final drying. In particular, while supported by an absorbent papermaking felt, the web is squeezed between the felt and the surface of a rotating heated cylinder (Yankee dryer) using a pressure roll as the web is transferred to the surface of the Yankee dryer for final drying. The dried web is thereafter dislodged from the Yankee dryer with a doctor blade (creping), which serves to partially debond the dried web by breaking many of the bonds previously formed during the wet-pressing stages of the process. Creping can greatly improve the feel of the web, but at the expense of a significant loss in strength.
More recently, throughdrying has become an alternate means of drying paper webs. Throughdrying provides a relatively noncompressive method of removing water from the web by passing hot air through the web until it is dry. More specifically, a wet-laid web is transferred from the forming fabric to a coarse, highly permeable throughdrying fabric and retained on the throughdrying fabric until dry. The resulting dried web is softer and bulkier than a conventionally-dried uncreped sheet because fewer bonds are formed and because the web is less compressed. Squeezing water from the wet web is eliminated, although the use of a pressure roll to subsequently transfer the web to a Yankee dryer for creping may still be used.
While there is a processing incentive to eliminate the Yankee dryer and make an uncreped throughdried product, uncreped throughdried sheets are typically quite harsh and rough to the touch compared to their creped counterparts. This is partially due to the inherently high stiffness and strength of an uncreped sheet, but is also in part due to the coarseness of the throughdrying fabric onto which the wet web is conformed and dried.
Therefore there is a need for a method for making an uncreped throughdried paper web which can provide improved combinations of sheet properties for a variety of different products.